1. SNS Coupler Shipping Plans
J. Mammosser, S. Stewart, B. Degraff , R. Huerto, Y. Kang, M. Howell

2. Overview: The Proton Power Upgrade (PPU) project is under way at SNS
SNS will process all RF couplers for the 7 new cryomodules that will be assembled at JLab
SNS will be responsible for the shipping of 15 pairs of conditioned RF couplers to Jlab for CM assembly

3. Current Status: CD1,3a has been awarded
30 new PPU couplers were procured (Jan 2019)
Couplers will be shipped to SNS starting in 6 months from now
SNS will clean, assemble, bake and condition these couplers and ship them to Jlab
Developing the shipment methodology is underway
Some design changes were made to the coupler design for PPU
Additional weight of the center conductor (~ 700g )

4. PPU Performance Requirements
Parameters
Original SNS high-beta
Cryomodule design
PPU high-beta cryomodule requirements
Eacc (MV/m)
(=EoTg, Tg: Transit time factor at β=0.81)
15.8
16.0*
Fundamental Power Coupler
(FPC) Rating (kW): peak and avg.
550, 50
700, 65*
External Q of fixed FPC
7 X105 ± 20%
8 X105 ± 20%
Cavity Material
High RRR niobium cells
Reactor grade end groups
High RRR for cell and
end groups
Higher-order Mode Couplers
(2) one at each end group
None*
Helium Vessel
Good engineering practice
Modified for code requirements*
*Operationally demonstrated in SNS
RRR = Residual resistivity ratio

5. Design Changes - FPCs
Charge 2
Two minor changes for the fabrication of new FPCs
The Inner Conductor wall thickness will increase from 3.5 mm to 7.5 mm to keep an operating temperature below the ones currently in operation
Increase of weight of inner conductor by ~700 g
The Center Conductor Length will be reduced by 1.5 mm (302.5mm tip to flange face) to increase the Qext

6. Shipping of Couplers After Conditioning
Current plans are to ship conditioned couplers on their bridge waveguide
After conditioning:
A leak check will be performed on the bake cart
Then an isolation valve will be closed on the bake cart and couplers will be transfer to a shipping cart
Vacuum space will then be vented to 2 psig nitrogen gas and isolated
Couplers will have full instrumentation for installation in string assembly
Once arriving at Jlab, the vacuum space will be pumped out and leak checked

7. Coupler assembly configuration

8. Coupler bridge waveguide

9. Bake Cart Configuration

10. Current Coupler Shipping Concept:
Coupler center conductor will be rigidly connected to the outer conductor with a plate bolted to both
This should minimize movement of the center conductor and prevent stress on the ceramic
Additional absorbing material on the air side will be investigated as well
Coupler will be shipped under nitrogen pressure (2psig)
Coupler cart will be similar in design to cleanroom cart and hold one bridge waveguide/ 2 RF couplers
FedX white glove van delivery service will be used
Two carts/ 4 couplers will be delivered at one time to JLab

11. RF Coupler Conditioning Assembly

12. Shipping Configuration
Stiffening
Plate
Shipping Configuration
Absorption
Material Option

13. Coupler Shipping Test Plan:
Coupler modes were modeled
Two PPU style RF couplers will be:
Cleaned and assembled
Baked
RF Conditioned and Leak checked
Vented to 2 psig nitrogen
Shipped to Jlab and back to SNS
Pumped and Leak checked
RF conditioned again
Vibration data will be collected

14. Conclusion: The PPU project at SNS is underway
30 new high power couplers will be conditioned and shipped to Jlab for assembly into 7 new cryomodules
Discussions on shipping of conditioned couplers to avoid damage is underway
Current plans are to ship coupler:
Mounted on bridge waveguide in pairs
Stiffening the mechanical system with a plate connecting the inner and outer conductors
Shipping under 2 psig nitrogen pressure